Process for curing asbestos-cement pipes



June 5, 1945. J. A. cANN PROCESS FOR GURING ASBESTOS-CEMENT PIPES VOriginal Filed May 25, 1941 4 Sheets-Sheet 1 FIG. l

F l. la,

Y PROCESS FOR-CURING ASBESTOS-CEMENT PIPES Griginal Filed May 23, 1941 4 Sheets-Sheet?! MMM Arm/MD5 June 5, 1945. J. A. CANN l 2,317,480

PROCESS FOR CURING ASBESTOS-CEMENT `PIPES Original Filed May 23, 1941 4 Sheets-Sheet 3 Arm/www3 J. A. CANN Original Filed May 23, 1941 PROCESS FOR CURING ASBESTOSCEMENT PIPES June 5, 1945.

PatentedgJune 5,

. l 2,371,450 f rnocnss Foa cunrntsnasroscmmm John Arthur Cann, Bickley,

Turner Newall Limited,

Rusland. :miml t0A Spotland, Rochlnl England, a company of Great Britain original application my es, v1941, serial No.

Divided 8nd this applicationlilay 14,

ma, semi No. 481,003. m Great prima may z claims. (cl. 25-154) t y g track along which .thefmandrels roll in passing 'I'his invention relates to the production of pipesfrom asbestos-cement or like material, that is to say, fibrous material and a binding agent that sets rigid from a plastic state. These pipes are commonly formed on mandrels, and at present it is the usual practice to loosen the pipes on the mandrels by a processv known as calendering while the asbestos-cement is still moist.

transfer the moist pipes to split wooden mandrels, and allow them to set and dry on these wooden mandrels. 'I'here is a risk of the pipes becoming slightly warped during this setting and drying. Moreover, it is necessary to maintain two sets of mandrels in use, and of course the transferirom the one mandrel to the other is an undesirable operation, although it is necessary under the present practice as the pipes take a long time to set. An important object of my invention is to provide a process bywhigh the pipes may be set dand dried. on the mandrels on which they are Q made, thus avoiding the necessity for transferring them to separate mandrels.

A further object of my invention is to provide for setting the pipes quickly at substantially atmospheric pressure.v

Yet another object of my invention-is to provide for handling the pipes before and during the setting without damaging them.

In proceeding in accordance with my inven tion, the coatings are loosened on the mandrels and then, while still on the mandrels on which they were formed, are placed at substantially atmospheric pressure in hot humid air. The setyting is accelerated by the heat, and whenthe pipes have set they are removed from the mandrels. Itis necessary .that the air should be humid, because, if it is not, water required for completely setting the cement or other binder will be extracted from the pipes by the atmosphere, and the pipes will be weakened. The temperature of the atmosphere should not exceed 150 F.,vsince above this temperature the asbesitos-cement tends to swell. On the other hand, if the temperature is low the setting time is prolonged. It is preferred to maintain the temperature at or above 125 F., as by this means setting takes place in under an hour.

'Ihe mandrels may advantageously be slowly rotated while they are in a hot humid atmosphere, as then any risk of the pipes sticking to the mandrels is eliminated.

In order to carry out the process of the invention, I have devised a novel. form of apparatuscomprising achamber containing a runway or through the chamber, means for engaging the mandrels and causing them to roll along the runway or track, and means for maintaining humid the atmosphere in the chamber.

My invention will best beunderstood from the following description of the preferred embodiments of it, taken in conjunction with the annexed drawings, in which:

Figures 1 and lla together form an elevation of one treating chamber with the side wall removed to show the internal parts;

Figure 2 is a section on the line II-II in Figure 1a;

Figure 3 is an elevation, similar to Figure 1 of another chamber;

Figure 3a is an elevation of the right-hand end of the chamber illustrated in Figure 3; and' Figure 4 shows part of a larger scale.

Referring rst to Figures 1 and 2, the chamber is a rectangular structure I which is Wholly this secondvchamber to closed except for an opening at each end. Each opening is closed by a. hinged door 3 having balance weights 4 i'lxed to arms which lie outside the chamber and clear it as they rock. Each door also has a builer 5 fixed to it.

The chamber contains an inclined runway in the form of 'two tracks 6 which extend through the end openings, the doors being shaped to accommodate these tracks. Coated vmandrels 2, with their coatings previously loosened by calendering, roll down the runway, the uncoated ends of the mandrels running on the tracks 6. The tracks each have upstanding outer ilanges 1 which 'act as guides for the mandrels. When v a. mandrel arrives at a door 3 it hits the buffer 5 and opens the door, so that it 'passes through automatically, the .door closing behind it.

Inside the chamber the mandrels are engaged bytwo rubber belts 8 which passaround rollers. Each belt is engaged by two end rollers, one of which, V9, is fixed to a shaft I0 driven through a chain wheel Il, `and the other of which, I2, is iixed to a shaft I3. Each belt is also engaged by intermediate rollers Il' carried by shafts I5. All these rollers serve to press the lower runs of the belts downwards into contact with the uncoated Y ends of the mandrels, so that the mandrels are caused to roll slowly through the chamber along the runway.

Asbestos-cement pipes naturally varyin di ameter, some being made .on mandrels only 4 inches in diameter and others made on mandrels that may be as large as 18 inches in diameter.

In order to allow mandrels of diiIerent sins to be treated, the end rollers Il and intermediate rollers I4 are made adjustable in position. Figure 1 shows in full lines their position and those of the belts for treating small mandrels, and in dotted lines the positions i'or treating large mandrels. The necessary adjustment is eiiected by making the shafts Il and Il slidable in guides i6 in the side walls oi the chamber.

The atmosphere in the chamber is maintained hot, e. g. at 125 F., and humid by means of a water bath 22 containing steam coils l1. Thus the coatings that form the pipes are set as the mandrels pass through the chamber.

In the chamber shown in Figures 3 and 4, the rubber belts are replaced by chain conveyors 23 having projecting arms Il which carry rollers i9. As each mandrel arrives it is engaged by a a pair of arms I8, as shown in Figure 4, and thus caused to travel through the chamber. The end chain wheels 20 over which the conveyors pass are made adjustable vertically by being mounted in guides 2i, so as to accommodate mandrels of different sizes. As an example, there may be five inches between successive arms and then the rollers will engage a 4" diameter mandrel as shown in full lines in Figure 4 and an 18" diameter mandrel as shown in dotted lines in the same figure. In the latter case the irictional engagement of the rollers Il with the top oi the mandrel is enough to cause the mandrel to roll along the rlmway.

In either of the chambers illustrated, the escape of humid air when the doors are opened may be reduced, if necessary, by the provision oi.'

r trap chambers, each with two doors, at each end.

This case is a division oi my co-pending application, Serial No. 894,909, now Patent No. 2,329,184 granted September 14, 1943.

I claim:

1. The process of producing asbestos-cement pipe comprising coating a solid mandrel with a layer of plastic asbestos-cement, loosening said plasticcoating on said solid mandrel, heat treating said loosened coating on said mandrel in a hot humid atmosphere by maintaining the temperature at or below 150 F. to prevent swelling and maintaining said temperature for a time effective to set said loosened coating.

2. The process o t producing asbestos-cement pipe comprising coating a mandrel with a. layer of plastic asbestos-cement, loosening said plastic coating on said mandrel, treating said loosened coating on said mandrel in a humid atmosphere and while continuing said treatment rolling said mandrel bearing the said loosened plastic coating for a time and at a temperature effective to set said coating and maintain the coating against warping during setting.

^ JOHN ARTHUR CANN. 

